Fiber-reinforced resins have excellent specific strength, moldability, and the like, and the application field thereof has been expanded. Specifically, fiber-reinforced resins have been studied for the application to general automobile body components, electrical equipment housing components, and the like, the mass production of which is expected.
In the application of fiber-reinforced resins to general automobile components or electrical equipment components, the development of fiber-reinforced resins with a glass fiber or a carbon fiber using a thermoplastic resin as a matrix has been progressed, and an increase in the fiber length of a reinforcing fiber contained in a molded product, and an increase in the content of a reinforcing fiber have been demanded. For example, PTL 1 proposes an automobile exterior component which is an injection molded product of a fiber-reinforced thermoplastic resin composition, wherein a reinforcing fiber in the molded product has a fiber length of 1.5 to 5.0 mm and a weight average distribution of 1 to 50%. Then, it is said that the reinforcing fiber in the molded product has a fiber length of 1.5 to 5.0 mm and a weight average distribution of 1 to 50%, preferably 5 to 50%, and a composition to be used for an automobile exterior component is obtained from a thermoplastic resin in an amount of 40 to 99% by weight and a reinforcing fiber in an amount of 60 to 1% by weight, preferably a thermoplastic resin in an amount of 50 to 75% and a reinforcing fiber in an amount of 50 to 25%.
General automobile components or electrical equipment components composed of such a fiber-reinforced resin have a shape in which a boss, a rib, or the like for attachment of various components is provided in a plate-shaped part, and in general, the plate-shaped part which forms a main body part is thin and has a large area, and a part which forms an additional part such as a boss or a rib has a complicated shape in many cases. Due to this, a production method capable of incorporating a reinforcing fiber having a long fiber length at a high volume content, and using a press molding method which is favorably used for production of a fiber-reinforced resinous component which is isotropic and has high strength and an injection molding method which is favorably used for mass production of a material having a complicated shape in combination has been proposed.
For example, PTL 2 proposes a production method for an integrally molded product including a step (I) in which a base material composed of a discontinuous reinforcing fiber and a resin is stacked, thereby forming a preform, a step (II) in which the preform having a charge ratio more than 100% is placed in a die and press molding is performed, and a step (III) in which after a sheet molded body obtained in the step (II) is inserted into an injection molding die, a thermoplastic resin is injection molded and integrated with the sheet molded body. It is said that according to this production method, by using a sheet molded body formed from a discontinuous reinforcing fiber and a resin as a primary molded body and integrating this molded body with a thermoplastic resin by injection molding, a thermoplastic resin molded body having high dynamic properties and a complicated shape can be easily obtained.
PTL 3 proposes a molding method for a fabric decorative resin product in which a transmissive sheet composed of a thermoplastic resin and a fabric sheet obtained by weaving a filament of the thermoplastic resin into a reinforcing fiber bundle are preformed by preheating and pressing in preforming dies, respectively, and these are overlapped with each other in an integrally molding die and hot-press molded to mold a decorative preform in which these are integrated with each other, and thereafter, the decorative preform is placed in an injection molding die, and a thermoplastic resin of the same quality as the thermoplastic resin is injection molded on a rear surface side, whereby a fabric decorative resin product is molded. It is said that according to this molding method, a fabric decorative resin product which is favorably used as a lightweight and highly rigid vehicle body component (for example, a cowl, or the like) can be molded economically by eliminating all steps such as a trimming operation and a post-installation operation for an attachment tool while maintaining the strength and design of the fabric sheet as they are.